Indo-1 AM is a fluorescent Ca²⁺ indicator (λ_ex=340 nm, λ_em=405/485 nm). In Vitro: Indo-1 AM is a fluorescent Ca²⁺ indicator with λ_ex=340 nm and λ_em=405/485 nm^[1]. In rabbit hearts that are exposed to Indo-1 AM, 72% of the dye is in the cytosol, and the remainder is associated with the mitochondria, microsomes and the nucleus^[2].